There are always sealing arrangements between the hoods and the regenerative mass and these take the form of sealing elements, such as sealing frames with wear shoes, which are held adjacent the end surfaces of the regenerative mass or slidingly pressed on them under resilient loading.
When the regenerative mass heats up distortion occur because it is not uniformly heated. It has a "hot end" and a "cold end". The effect of this is that the sealing frames have to be adjustably positioned.
It is known in the art to spring-load pins which bear the frames so that if the mass comes into contact with them, they are driven back. This, however, results in increased wear of the wear shoes, and the range of movement available may not be sufficient to allow adequately, in some conditions arising, for the amount of adjustment which is desirable.
An automatically responsive element for causing the adjustment of rigid sealing elements, here sealing plates, at one or both ends of a rotation regenerative mass has previously been proposed in United Kingdom Patent No. 1058627 and U.S. Pat. No. 3,246,687. In this arrangement a thermally expansible element preferably in the form of a duct for gases is arranged parallel to the axis of the rotary mass regenerator and is linked at the level of at least one of the ends of the regenerative mass with the sealing plate. In one arrangement the other end of the duct is firmly anchored to a fixed casing of the mass, while in an alternative arrangement each end of the duct is floating and secured to the respective sealing plate. The effect on temperature rise is to drive the sealing plate or the sealing plates away from the respective ends of the regenerative mass.
The effect however of temperature rise on the mass itself is to cause it to adopt a calotte shape with the hot end being convex and the cold end concave. So it would be desirable on temperature rise that the hot end sealing plate should in fact be drawn towards the regenerative mass and not pushed away from it. Thus, the arrangement shown in the U.K. Patent No. 1058627 while having the effect which that specification states it has, that of reducing the possibility of interference between the rotor and the sealing plate, also has the effect of increasing the gap between at least one of the sealing plates and the end of the mass over which it is placed.
This duct being a simple expansion part which is associated with the ducts and hoods means that the extent of the adjusting movement cannot be influenced freely but is limited to what can be used in this constructional part at the temperatures which are to be sensed.
It is to be noted that the control selected for the determination of the amount of thermal expansion is the cooled gas that has passed through the regenerative mass and has given up its heat to it. This temperature under normal operating conditions is comparatively low and does not offer much sensitivity for the available response of the temperature responsive device. Therefore, in normal operation the response of this device offered is negligible and cannot be considered as a control for seal-setting. Only in case of an abnormal rise of the cold end temperature, as it may happen during "startup", "shutdown" or "when the flow of air or other cool fluid through the heat exchanger has been substantially curtailed" the outlet temperature of the cooling fluid may rise to a degree that the temperature-sensitive device will respond. In this case the response will act not for an optimum seal-setting but in the contrary such, that the seals are moved completely away from the end faces of the regenerative mass.
The present invention is concerned with providing for automatic adjustment of the limits of setting of the sealing elements at the end faces of the regenerative mass in accordance with the actual operating conditions at any given time, and for ready selection and control of that adjustment.